Jet propulsion nozzle



Sept. 1, 1964 s. F. SMITH ETAL JET PRoPuLsIoN NozzLE 4 Sheets-Sheet 1 Filed June 26, 1961 r' MW Attorneys Sept- 1, 1964 s. F. sMlTH ETAL 3,146,584

JET PROPULSION NOZZLE Filed June 26, 1961 4 Sheets-Sheet 2 Sept. 1, 1964 s. F. SMITH ETAL JET PRoPuLsIoN NozzLE 4 Sheets-Sheet 3 Filed June 26, 1961 B Y Z I y Attorneys Sept' 1, 1964 s. F. SMITH ETAL 3,146,584

JET PRoPULsIoN NozzLE Filed June 26, 1961 4 Sheets-Sheet 4 l A ttorn ys United States Patent O 3,146,534 JET PROPULSIN NOZZLE D Stanley Frank Smith, Derby, England, David Craigre,

Edinburgh, Scotland, and .lohn Gregory Keenan, Derby,

England, assignors to Rolls-Royce Limited, Derby, England, a company of Great Britain Filed .lune 26, 1961, Ser. No. 119,674 Claims priority, application Great Britain July 1, 1960 7 Claims. (Cl. Gil-35.6)

This invention concerns a jet propulsion nozzle assembly adapted for use at supersonic jet velocities.

According to one particular aspect of the present invention, there is provided Aa jet propulsion nozzle assembly adapted for use at supersonic jet velocities comprising a nozzle member and a body extending downstream of the nozzle member, said body being provided with means having a concave surface which constitutes a smoothly curved extension of the downstream end of an outer wall of the nozzle member and which controls the expansion of the jet gases downstream of the nozzle member.

Preferably the nozzle member has a substantially rectangular downstream end and the said concave surface constitutes an extension of the uppermost of the outer walls of the rectangular downstream end.

In an alternative arrangement the said concave surface constitutes an extension of the lowermost of the outer walls of the nozzle member of said rectangular downstream end.

According to another aspect of the present invention, there is provided a jet propulsion `nozzle assembly adapted for use at supersonic velocities comprising a nozzle member, having a substantially rectangular downstream end, and a body extending downstream of the nozzle member, said body being provided with means having a concave surface which constitutes a smoothly curved extension of the downstream end of an outer wall of the nozzle member and which controls the expansion of the jet gases downstream of the nozzle member, the tangent to the internal surface of the nozzle member at the lip thereof being disposed at substantially the calculated angle of refraction for the design-Mach number and intersecting the nozzle axis downstream of the nozzle member.

The term nozzle axis where used throughout this specication is intended to mean a reference line, lying in the plane of symmetry of the nozzle and parallel to the axis of symmetry of the jet propulsion engine with which the nozzle is used, the reference line being a distance a from the lip of the nozzle member. The value of ais equal to the product of Ra-ro where Ra is the ratio of the exit llow area to the throat area, known from the chosen value of the Mach number, M, and the exhaust gas properties, and ro is the depth of the throat from the lip of the nozzle member measured along the throat plane.

The term axial where used throughout this specification is intended to mean parallel to the nozzle axis.

Means are preferably provided to allow for relative thermal expansion between the nozzle member and the said body. rIhus the said body may carry an upstream concave-surfaced member and a downstream concavesurfaced member whose adjacent ends overlap and are slidable over each other, the upstream concave-surfaced member being connected to the nozzle member so that relative thermal expansion between the nozzle member and the said body is accommodated by sliding movement between the said adjacent ends.

The invention also comprises an aircraft provided with a jet propulsion engine having a nozzle assembly as set forth above.

3,146,584 Patented Sept. l, 1964 ICC Preferably the downstream end of the said concave surface substantially merges into the surface of the aircraft wing or fuselage.

The engine may be carried from the aircraft by means including a sliding connection such as accommodates relative thermal expansion therebetween.

Thus the engine may be provided with a thrust reverser and the nozzle member may be connected to the thrust reverser by a jet pipe which is carried from the aircraft by the said sliding connection.

The aircraft may be provided with a plurality of engines having similar nozzle assemblies which are arranged side by side.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which:

FIGURE l is a diagrammatic perspective view of a supersonic aircraft provided with engines having jet propulsion nozzles according to the present invention,

FIGURE 2 is a diagrammatic side elevation of the airv craft shown in FIGURE l,

FIGURE 3 illustrates, to a larger scale, part of the construction shown in FIGURE 2,

FIGURES 4 and 5 are views taken respectively in the direction of the arrows 4, 5 of FIGURE 3,

FIGURE 6 is a perspective View illustrating the construction of a ramp forming part of the structure shown in FIGURE 3,

FIGURE 7 .is a longitudinal section through one of the jet propulsion nozzles,

FIGURE 8 is a section taken on the line 8 8 of FIG- URE 7, and

FIGURE 9 is a diagrammatic sketch of the propulsion nozzle showing the various angles required in determining the geometry of the nozzle.

Referring to the drawings, a supersonic aircraft 1? has wings 11 beneath each of which is mounted a substantially box-shaped cowling 12. The Cowling 12 is divided by internal walls 13 into three longitudinally extending compartments 14 each of which houses a gas turbine, jet reaction, forward propulsion engine 15.

Each engine 15 comprises in flow series an air intake 16, compressor 17, combustion equipment 18, turbine 20, turbine exhaust duct 21, jet pipe section 22, thrust reverser23, and nozzle sections 24, 25, 26, 27 which collectively constitute a convergent nozzle.

The thrust reverser 23, which is adapted, when brought into operation, to direct the jet gases past deflector vanes 28, is mounted on trunnions (not shown) fxedly carried by aircraft main beams 30. The jet pipe section 22 lloats (by means not shown) so as to accommodate itself to any misalignment between the jet pipe section 22 and the thrust reverser 23.

The nozzle sections 24-27 are bolted to each other, the nozzle section 24 being bolted to the thrust reverser 23 and having a circular cross-sectional shape at its upstream end. The nozzle section 27, and also the downstream end of the nozzle section 26, has a Lflattened or horizontally elongated rectangular cross-sectional shape, the aircraft main beams 3@ being cut away at 31 to permit the nozzle section 26 to extend laterally outwardly thereof.

rIhe rectangular shape of the downstream ends of the nozzles of the engines 15, permits the nozzles of the three engines to be disposed immediately alongside each other. No partition walls are provided to separate the various jets which issue from the three nozzles, but end walls 29 confine the jets laterally.

The nozzle sections 26, 27 are supported from the beams 30 by a strap 32 (FIGURE 7). The strap 32 is connected to trunnions 33 of trunnion blocks 34. The blocks 34 are axially slidable in guides 35, the latter be- Zt ing bolted to the beams 34). Thus accommodation is provided for relative thermal expansion between the nozzle sections 24-27 and the aircraft beams 3l).

The nozzle section 27 is provided with guide vanes 36 of aerofoil shape to promote smooth longitudinal jet flow therethrough. The nozzle section 27 is also provided with an adjustable flap member 37 which is pivoted at 38, pivotal movement of the flap member 37 about the pivot 38 altering the effective cross-sectional area of the nozzle section 27 which is open to jet flow. The liap member 37 is pivotally connected at 40 to links 41 which are pivotally connected to bell crank levers 42. The latter have a pin and slot connection 43 with screw jacks 44 which are operated by an air motor (not shown).

Mounted about the downstream end of the nozzle section 27 is a strap 45 which is pivotally secured to links 46. The links 46, at their ends remote from the strap 45, are connected to trunnions 47 of trunnion blocks 48, the latter being axially slidable in guides 50. The guides 50 are secured to a ramp structure 51 which is secured to the downstream ends of the aircraft beams 30.

The internal construction of the ramp structure 51 is shown in FIGURE 6 from which it will be noted that the ramp structure is braced by a series of internal walls 52.

The links 46 carry a concave-surfaced skin 53 whose upstream end is in sealing contact with and forms a smooth continuation of the uppermost of the outer walls of the nozzle section 27. The downstream end of the skin 53 overlaps but is in scaling contact with a concavesurfaced skin 54, the arrangement being such as to permit relative axial movement between the skins 53, 54. The skin 54, and a concave-surfaced skin 55 arranged downstream thereof and sealed thereto, are carried by the ramp structure 51. The skin 55 is arranged substantially to merge into the surface of the wing 1l. The skins 53, 54 have stilfeners 56 bearing against pads 57 carried by the ramp structure 51. Relative thermal expansion between the nozzle sections 24-27 and the aircraft beams 30 therefore merely causes sliding of the downstream end of the skin 53 over the upstream end of the skin S4.

The underside of the ramp structure 51 is provided with a shield 58, backed by a thermal insulation blanket 66, to protect the structure 51 from any gas leaking past the skins 53-55.

As will be seen :from FIGURE 9, the upper surface 66' of the ramp structure 5l constitutes a plane containing the nozzle axis 66 (as hereinafter defined). The nozzle section 27 has at its downstream end a lip 62 formed so that the tangent 63 to the internal surface of the section 27 at the lip 62 intersects the nozzle axis 66 downstream of the nozzle section 27. The tangent 63, moreover, is disposed at an angle 6 to the nozzle axis 66, the angle constituting the expected angle of refraction through which the jet gases will be turned at the boundary with the atmosphere. The value of the said angle 0 may be calculated from the equation where M is the jet Mach number, and Iy is the ratio of the specific heats of the jet at constant pressure and volume. Thus for example, if M is 2 and 'y is 1.4, the angle of refraction 0 is 261/2 approximately.

The throat 64 of the nozzle section 27 lies in the plane of the downstream end of the latter and the tangent 65 to the skin 53 at the intersection of the plane 64 therewith makes an angle with the nozzle axis 66 equal to the aforementioned refraction angle 0.

If a Mach plane 67 is drawn downstream starting from the lip 62 at an angle to the axial direction, the angle n being determined from the equation where M is the design Mach number, then at the design Mach number, the flow downstream of the plane 67 is all axial. Such a plane is hereinafter referred to as a Mach lane.

p The skin 53, 54, 55 begins tangential to 65 and in an ideal design ends parallel to the nozzle axis 66 at the point where the skin meets the final Mach plane (67), on the nozzle axis 66.

The area of the nozzle throat 64 is equal to the product of the nozzle total width and ro, which is the depth of the throat from the lip 62 measured along the throat plane 64. If the perpendicular distance from the nozzle lip 62 to the axis 66 is a, and if the ratio of the exit flow area to the throat area, known from the chosen value of M and the exhaust gas properties, is Ra, then the ratio a/rU can be found from the equation,

since the jet gases do not expand perpendicularly to the plane of FIGURE 9, due to the end walls 29 which contine the jet gases laterally.

The optimum profile of the skin 53, 54, 55 is readily determined by drawing a series of construction lines radiating from the lip 62 to intersect the skin and arranging that each of these intersections shall be at a distance r from the lip, the distance r varying with the angle 10 between each construction line and the throat line 64 as in the following formula:

Preferably the skin 53, 54, 55 should extend downstream to a point as near as practicable to the final Mach plane 67.

The engines 15, instead of being mounted beneath the wings 11 as shown, may be mounted beneath the aircraft fuselage 61 or may be mounted above the wings 11 or fuselage 61.

The nozzle assembly described above has the advantage over a conventional diverging nozzle that, at the design Mach number, it has very much less surface area exposed to the supersonic part of the jet stream so that friction losses are diminished and, at Mach numbers less than design, there is no possibility of a wasteful internal shock wave such as occurs with the conventional nozzle.

We claim:

1. An aircraft provided with a jet propulsion engine having a nozzle assembly adapted for use at supersonic velocities comprising: a nozzle member having a substantially rectangular downstream end, and a body extending downstream of the nozzle member, said body being provided with means having a concave surface which constitutes a smoothly curved extension of the downstream end of an outer wall of the nozzle member and which controls the expansion of jet gases downstream of the nozzle member, said nozzle member having a lip at the downstream end thereof defining a throat thereof, said nozzle member having a nozzle axis lying in a plane of symmetry of the nozzle member and parallel to the axis of symmetry of the jet propulsion engine, the nozzle axis being a distance a from the lip of the nozzle member where where with Ra being the ratio of exit flow area to throat area for a chosen value of Mach number M and exhaust gas properties, and ro is depth of said throat from said lip of the nozzle member measured along a plane of the throat, the internal surface of said nozzle member at the lip thereof having a tangent thereto disposed at substantially an angle of refraction 6, measured from the nozzle axis and calculated for the chosen value of Mach number M, said tangent intersecting said nozzle axis downstream of the nozzle member, said concave surface of said body merging into the surface of the aircraft.

2. An aircraft as claimed in claim 1 wherein the angle of refraction H is calculated from the equation 7+ l -1 v 1 z -1 6-\/7 1tan v+1(M 1) tan w/M l where M is said Mach number and Fy is the ratio of specific heats of the jet at constant pressure and volume.

3. An aircraft as claimed in claim 1 in which the nozzle assembly is carried from the aircraft by means including a sliding connection which accommodates relative thermal expansion therebetween.

4. An aircraft as claimed in claim 3 in which the nozzle assembly is provided with a thrust reverser, the nozzle member being connected to the thrust reverser and being carried from the aircraft by the said sliding connection.

5. A jet propulsion nozzle assembly adapted for use at supersonic velocities comprising a nozzle member having a substantially rectangular downstream end, and a body extending downstream of the nozzle member, said body being provided with means having a concave surface which constitutes a smoothly curved extension of the downstream end of an outer wall of the nozzle member and which controls the expansion of jet gases downstream of the nozzle member, said nozzle member having a lip at the downstream end thereof defining a throat thereof, said nozzle member having a nozzle axis lying in a plane of symmetry of the nozzle member and parallel to the axis of symmetry of the jet propulsion engine, the nozzle axis being a distance a from the lip of the nozzle member where with Ra being the ratio of exit ow area to throat area for a chosen value of Mach number M and exhaust gas properties, and ro is depth of said throat from said lip of the nozzle member measured along a plane of the throat, the internal surface of said nozzle member at the lip thereof having a tangent thereto disposed at substantially an angle of refraction 0, measured from the nozzle axis and calculated for the chosen value of Mach number M, said tangent intersecting said nozzle axis downstream of the nozzle member.

6. A jet propulsion nozzle assembly adapted for use at supersonic velocities comprising a nozzle member having a substantially rectangular downstream end, and a body extending downstream of the nozzle member, said body being provided with means having a concave surface which constitutes a smoothly curved extension of the downstream end of an outer wall of the nozzle member and which controls the expansion of jet gases downstream of the nozzle member, said nozzle member having a lip at the downstream end thereof defining a throat thereof, said nozzle member having a nozzle axis lying in a plane of symmetry of the nozzle member and parallel to the axis of symmetry of the jet propulsion engine, the nozzle axis being a distance a from the lip of the nozzle member where with Ra being the ratio of exit flow area to throat area for a chosen value of Mach number M and exhaust gas properties, and ro is depth of said throat from said lip of the nozzle member measured along a plane of the throat, the internal surface of said nozzle member at the lip thereof having a tangent thereto disposed at substantially an angle of refraction 0, measured from the nozzle axis and calculated for the chosen value of Mach number M, said tangent intersecting said nozzle axis downstream of the nozzle member, and means to allow for relative thermal expansion between the nozzle member and the said body.

7. A jet propulsion nozzle assembly as claimed in claim 6 in which the said body carries an upstream concavesurfaced member and a downstream concave-surfaced member whose adjacent ends overlap and are slidable over each other, the upstream concave-surfaced member being connected to the nozzle member so that relative thermal expansion between the nozzle member and the said body is accommodated by sliding movement between the said adjacent ends.

References Cited in the tile of this patent UNITED STATES PATENTS 2,828,607 Johnson Apr. l, 1958 2,968,920 Wayne et al Jan. 24, 1961 2,972,230 Conklin et al. Feb. 21, 1961 2,982,496 Creasey et al. May 2, 1961 3,019,601 Sens Feb. 6, 1962 3,034,296 Keen et al May 15, 1962 3,080,711 Connors Mar. 12, 1963 

5. A JET PROPULSION NOZZLE ASSEMBLY ADAPTED FOR USE AT SUPERSONIC VELOCITIES COMPRISING A NOZZLE MEMBER HAVING A SUBSTANTIALLY RECTANGULAR DOWNSTREAM END, AND A BODY EXTENDING DOWNSTREAM OF THE NOZZLE MEMBER, SAID BODY BEING PROVIDED WITH MEANS HAVING A CONCAVE SURFACE WHICH CONSTITUTES A SMOOTHLY CURVED EXTENSION OF THE DOWNSTREAM END OF AN OUTER WALL OF THE NOZZLE MEMBER AND WHICH CONTROLS THE EXPANSION OF JET GASES DOWNSTREAM OF THE NOZZLE MEMBER, SAID NOZZLE MEMBER HAVING A LIP AT THE DOWNSTREAM END THEREOF DEFINING A THROAT THERE- 